1. Field of the Invention
This invention relates to an ultrasound-imaging system employing an ultrasound probe to be inserted into patient's body for ultrasound examination or diagnosis.
2. Prior Art
The ultrasound imaging system is generally composed of an ultrasound transmitter-receiver or transducer and an ultrasound image observation terminal, the observation terminal including ultrasound signal transmission and reception circuits, a signal processing circuit for processing the ultrasound echo signals received by the reception circuit, and a monitor for viewing an ultrasound image. The ultrasound imaging systems of this sort are widely used in the medical field, transmitting ultrasound energy into a body through an ultrasound transducer and transferring return signals to the signal processing circuit of the ultrasound observation terminal to display the information concerning intracorporeal tissue as an ultrasound image on the monitor screen.
In this connection, for the purpose of improving the accuracy and functions of the ultrasound examination or diagnosis, there have come into use ultrasound examination systems which are arranged to insert an ultrasound transducer into patient's body to transmit and receive ultrasound signals at a position close to an intracorporeal structure to be examined or diagnosed. Further, as proposed in U.S. Pat. No. 4,802,487, there have also been developed endoscopic ultrasound imaging systems which, for three-dimensional examination, provides, in addition to the optical examination and diagnosis through an endoscope, the ultrasound information on the tissue of an intracavitary structure of interest by inserting into patient's body a narrow ultrasound probe or catheter having an ultrasound transducer at its tip end under guidance of an endoscope. For this purpose, the ultrasonic probe is inserted into a biopsy instrument channel which is usually provided in the endoscope for insertion of forceps or other treating instruments, protruding the ultrasound transducer from the tip end of the biopsy channel for transmission and reception of ultrasound energy.
In such ultrasound examination or diagnosis, it is the general practice to bring the ultrasound transducer into intimate contact with an intracavitary wall or the like or to position the ultrasound transducer to face an intracavitary wall through intervention of an ultrasound transmissive medium like water, holding the ultrasound transducer in certain direction and posture with respect to the intracavitary wall during transmission and reception of ultrasound waves. Besides, in case of an ultrasound imaging system using an endoscopically inserting ultrasound probe, it is necessary to adjust the direction and posture of the ultrasound transducer through remote control. For this purpose, a manual rotating mechanism is provided in association with a rear end portion of the catheter or insert section of the probe outside the proximal end of the biopsy channel of the endoscope, torsionally turning the catheter through manipulation of the rotating mechanism for controlling the direction and posture of the ultrasound transducer. In case of a mechanical radial scan type, the insert section is connected to a mechanical rotational drive means.
However, when torsionally turning the insert section of the probe in the biopsy channel of the endoscope directly by a manual operation, a difficulty is often encountered in transmitting the turning moment smoothly to the ultrasound transducer due to inferior operationability particularly in controlling the direction of the transducer. Besides, as a cable from the ultrasound transducer is normally blocked against rotation at its proximal end which is connected to an operating unit, the cable is twisted in the proximal portion when it is operated to rotate the ultrasound transducer, instabilizing and causing positional deviations of the ultrasound transducer by the righting force of the twisted cable portion. Accumulation of such twist takes place when the operation is repeated, inviting further deteriorations in controllability and, in case of accumulation of a large number of twists, causing a disconnection in wiring cable which is inserted in a sheath material of the probe.
Further, in controlling the direction and posture of the ultrasound transducer, it is often the case that the operator of the ultrasound imaging system does not pay much attention to the twisting of the cable. For controlling the posture of the ultrasound transducer, it is the general practice to turn the cable in a certain predetermined direction, so that the cable is usually twisted to a considerable degree, in spite of the instabilization of the position and posture of the ultrasound transducer and high possibility of wire disconnection in the cable. In this regard, it is conceivable to restrict the rotational angle of the cable, which however gives rise to a problem of deterioration of controllability in controlling the direction and posture of the ultrasound transducer.